As disclosed in Sterling Drug's U.S. Pat. Nos. 3,753,993 (Lesher et al.), 3,907,808 (Lesher and Carabateas), and 4,118,557 (Lesher), it is known that antibacterial 1-alkyl-1,4-dihydro-4-oxo-7-pyridinyl-3-quinolinecarboxylic acids can be prepared from 4-(3-aminophenyl)pyridine. It is also known that this route to the bactericides, as disclosed, is less economical than might be desired.
From Mitscher et al., "Quinoline Antimicrobial Agents. 1. Versatile New Synthesis of 1-Alkyl-1,4-dihydro-4-oxo-3-quinolinecarboxylic Acids," Journal of Medicinal Chemistry, 1978, Vol. 21, No. 5, pp. 485-489, It is also known that antimicrobial agents related to the aforementioned bactericides can be prepared from the appropriate isatoic anhydrides.
It would be desirable to be able to prepare the antibacterial agents of Lesher, Lesher et al, and Lesher and Carabateas by a route similar to that employed by Mitscher et al. However, although, as indicated in copending application Ser. No. 511,887, filed July 8, 1983, in the name of Thomas J. Walter (Walter), this route to the antibacterial agents can be employed when 4-(4-alkyl-3-nitrophenyl)pyridines are utilized, it has previously been found difficult to convert the 4-(4-alkyl-3-nitrophenyl)pyridines to the acids, salts, or esters required for conversion to suitable isatoic anhydrides. Thus, a satisfactory method of synthesizing a material capable of being converted into a suitable isatoic anhydride has not previously been proposed.